A combine harvester is a machine that is used to gather, thresh, and clean a wide range of grain crops while returning the straw, chaff and material other than grain (MOG) back to the earth in a single pass over the field. Typically, a combine harvester gathers the crop from the field with a header and transports the crop by means of a feeder house to a threshing and separating device located inside the combine. Generally, threshing refers to removing grain, beans, seeds or kernels, hereinafter referred to as just grain, which are desired to be collected, from husks, cobs, pods, stems, straw, and other portions of the plants being harvested, which are to be discarded.
The threshing and separating mechanism of the combine typically consists of a rotating threshing rotor or cylinder to which grooved steel bars, commonly referred to as rasp bars or threshing elements, may be bolted. These rasp bars thresh and aid in separating the grains from the chaff and straw (sometimes referred to as residue) through the rubbing action of the rotor or cylinder against the concaves, i.e., shaped “half drum,” that may also be fitted with angled steel bars (e.g. rub bars) and a meshed grill, through which grain, chaff and smaller debris may fall, whereas the straw, being too big or long, is carried through to the outlet. Typically, the rotor or cylinder speed may be variably adjustable and the distance between the rotor or cylinder and concave may be finely adjustable laterally and together, to achieve optimum separation and output.
In an axial flow combine, where the rotor is axially mounted, this threshing and separating system serves a primary separation function. The harvested crop is threshed and separated via a mechanical rubbing action as it is conveyed between a longitudinally arranged rotor and the inner surface of an associated chamber comprising threshing and separating concaves. The cut harvest material spirals rearward and is conveyed along a helical path along the inner surface of the chamber until substantially only larger residue remains. When the residue reaches the end of the threshing rotor, it is expulsed out of the rear of the combine, often via a straw beater, straw chopper and/or straw spreader. Meanwhile, the grain, chaff, and other small debris falls through the concaves and grates onto a secondary separating and cleaning system. For ease of reference, this smaller particulate harvest material that contains the grain and chaff is referred to as threshed crop and the secondary separating and cleaning system is referred to simply as the cleaning system.
In the cleaning system the threshed crop is further processed to separate-the grain from the chaff by way of a winnowing process. The objective of this winnowing process is for the clean grain to fall via gravity through a series of sieves where it will be collected and elevated to a temporary storage device while the chaff and (MOG) is transported to the rear of the machine and expelled back to the field. On most modern combines, the cleaning system is composed of a conveyor system, a plurality of reciprocating sieves, and a fan blower. The conveyor system, which may be a plurality of augers, a reciprocating grainpan, or another suitable conveying device, receives the threshed crop from the threshing system and delivers it to front part of the sieves where the winnowing process begins. Each sieve is a generally planar surface with a plurality of holes or openings appropriately sized such that the desirable grain can fall through while the larger undesirable chaff particles cannot. The fan blower produces an air blast which is generally directed upward and rearward through the sieves to assist with the winnowing process by levitating the chaff material, which is generally less dense than the grain, thereby improving the probability of sieving the grain. Most cleaning systems are composed of multiple layers of sieves, generally two, wherein the upper sieve, herein referred to as the grain bed has larger openings to capture all of the grain and inevitably some smaller, denser bits of chaff while the lower sieve has smaller openings such that more thorough sieving of the clean grain can occur. Any material that passes through the upper sieve and is transported to the rear of the lower sieve without passing though is referred to as tailings. In many harvesters, the grain bed may include one, some, or several sections of upper sieves. In some embodiments, the upper sieves may also include pre-sieves. For ease of reference, material traveling along the grain bed in the cleaning system will be described as simply crop material, since it may include threshed crop and returned tailings.
The chaffing and sieving system on most modern combines operates on the assumption that the conveyor system delivers fairly uniform grain across the width of the grain bed. For example, the chaffing process optimally works on an assumed range of thicknesses of separated crop material in a grain bed, which allows fans to blow off the chaff. If the thickness of the crop material in the grain bed is too thick, the airflow supplied will be insufficient. Furthermore, the sieves may be unable to process the grain quickly enough, such that if threshed crop and/or tailings are delivered too quickly to one portion of the sieve area in the grain bed, the system may clog or the yield of the grain delivered to other portions of the cleaning system may be reduced. If the crop material is too thick or moves to fast in the grain bed for all grain and/or MOG to penetrate the sieves, the grain and MOG, herein further named heavy crop matter, when described in the grain bed, will undesirably exit the rear of the grain bed and result in heavy crop matter loss.
In many cases, it is desired for material that could not penetrate the lower sieves, the tailings, to be threshed and/or cleaned again. In some harvesters, threshing and/or cleaning of the tailings is accomplished by conveying them to one side of the combine with an auger. The tailings are then carried by a conveyor, typically a paddle and chain conveyor, back to the combine threshing mechanism. Some combines have used a rethreshing device, which is separate from the threshing system and helps save capacity on the threshing system by rethreshing the tailings separately from new crop coming into the combine. The auger feeds material into the rethreshing device and then the material is conveyed back to the cleaning system. Both single impeller/blowers and augers have been used to convey this material back to the cleaning system. These rethreshing devices are usually convertible, enabling the operator to manipulate the machine to be more or less aggressive, depending on the vulnerability of the grain to damage, during processing.
In other harvesters, the tailing are conveyed by an auger to a tailings conveyor in proximity to the cleaning system. The tailings conveyor, in some harvesters, incorporates a series of impellers, or fans, to lift tailings up the side of the cleaning system and then distributes the grain back to the grain bed for re-cleaning.
The upper sieves of a cleaning system are normally composed of separate lengthwise sections separated by upstanding dividers which are operable to allow only for restricted lateral movement of crop material along the grain bed of the cleaning system. When distributing the tailings from a transverse side of the harvester under a sharp angle onto a top layer of the crop material on the upper sieves, the grain kernels contained in said tailings have a tendency to penetrate said layer and to continue their trajectory until movement thereof is restricted by a divider, delimiting, in that direction, the section in which the grain kernels have been projected. As a result of this action, returned tailings start to accumulate on one side of a section as additional heavy crop matter, whereas chaff material which is much lighter than the heavy crop matter, is dispelled to the other transverse side of the section whereby the even distribution of heavy crop matter and chaff transversely of a section becomes disturbed. It is clear that concentrating the grain on one side of a section and the chaff material at the other side thereof, results in overloading and/or underloading of the respective sections on the grain bed ultimately leading to heavy crop matter losses at the rear of the grain bed due to lateral non-uniform loading of crop material across the grain bed. The overloading or uneven loading in the grain bed, demonstrates uneven distribution of crop material in the grain bed, and dampens the effectiveness of the fan to blow chaff from crop material in the grain bed. Blown air from the fan moves through the grain bed in a path of least resistance so that uncovered portions of the grain bed receive most blown air and heavily covered portions receive little blown air. Thus, cleaning on the grain breaks down.
Conventional operation procedures recommend that an operator visually and manually inspect the grain bed to determine if crop material is uniformly distributed across the grain bed. Non-uniform distribution of crop material across the grain bed typically occurs in combines equipped with axially mounted rotors or when the combine is operated on slopes. Presently, the operator is required to perform a kill stall, whereby the operator stops the combine, gets out of the cab, accesses the grain bed or conveyor system, and checks for uniform or uneven distribution as well as for grain or MOG loss over the rear side of the cleaning system. If the grain bed is uneven, the operator can manually adjust mechanisms in the threshing and conveyor system until crop material entering the grain bed results in substantially uniform distribution of crop material in the grain bed. This process is labor intensive and requires a skilled operator.
What is needed is a means to sense crop material distribution in the grain bed so as to optimize a tailings distribution system to improve the total distribution of crop material on a grain bed or conveyor system in a cleaning system.